1. Field of the Invention
This invention relates to an end effector for use with a robot, and, more particularly, to a multi-finger end effector in which each finger is independently operated hydraulically to engage parts of varying size and weight by a hydraulic actuating system. Only after all of the fingers contact the part does the hydraulic system pressure increase to permit prehension.
2. Description of the Prior Art
General purpose robots can perform a variety of tasks and manipulate parts of different geometry and weight. However, existing end effector or robotic hand designs are limited in that only a relatively few different part geometries and weights can be accommodated by a single end effector. This means that a set of different end effectors are required by the general purpose robots to handle a wide range of part geometries and weights.
U.S. patent application Ser. No. 915,596, now U.S. Pat. No. 4,799,853, filed Oct. 6, 1986, to Wrobbel et al, entitled "Self-Centering End Effector", and commonly assigned to the assignee of this invention discloses an apparatus which acquires individual articles having a cylindrical aperture therein from a supply of roughly aligned articles in a storage bin. The apparatus grips the article on the interior wall on the aperture therein, retracts the article from the storage bin, and moves it to a receiving member which aligns the longitudinal axis of the cylindrical aperture of the article parallel or coincidential with the longitudinal axis of the receiving member.
U.S. Pat. No. 4,627,654 to Van Oost discloses an articulated parallelogram gripper for use by a robot to grasp the inner or outer diameter of circular pieces. The gripper comprises three separate parallelogram linkage systems concurrently actuated by a hydraulic cylinder to move an arm fixedly attached thereto towards and away from the axis of the hydraulic cylinder. The linkage systems are positioned 120 degrees apart around the axis of the hydraulic cylinder. Each fixedly attached arm of the linkage systems has a finger extending therefrom which is parallel to the hydraulic cylinder axis, so that concurrent movement of the fingers are towards and away from the axis of the hydraulic cylinder. Thus, the fingers may grip the outer diameter of a cylindrical object or the internal diameter of a cylindrical opening or bore of an object to be moved.
U.S. Pat. No. 4,623,183 to Aomori discloses a robotic hand having three rotatable, coaxial sleeves with each having a decreasingly smaller diameter. The sleeves are positioned one inside the other and are independently rotatable by separate motors. Each sleeve has a pivotably mounted finger cantilevered therefrom and means to actuate the distal end of the finger towards and away from the sleeve's common axis. Selective independent rotation of the sleeves enables the fingers to grasp and/or support various cylindrically shaped parts.
U.S. Pat. No. 3,901,547 to Skinner discloses a multiple prehension robotic mechanism having three finger assemblies mounted on a base which can approach, contact, or pass one another during a prehensile operation. The fingers can be actuated by individual drive means or by one drive means operatively connected to all of the fingers for simultaneous pivoting into engagement of variously shaped objects.